Cavity-backed aperture antennas with dielectric and magnetic overlay

A method is presented for a full wave analysis of an aperture antenna backed by a rectangular cavity. The antenna may be covered by one or more dielectric and magnetic layers. The aperture antenna may be arbitrarily shaped but must be small compared to the cross section of the cavity. The analysis includes ohmic, dielectric, and magnetic losses in the cavity as well as in the overlay. Deriving a modified magnetic field integral equation, the treatment of the cavity and of the layered overlay is separated. A dyadic Green's function describing the topology of the cavity is formulated in the space domain. Another dyadic Green's function for the layered overlay is derived in the spectral domain. Subsequently, the integral equation is solved by the method of moments. The theoretical treatment is worked out for arbitrarily shaped apertures. Finally, the proposed method is applied to narrow slot antennas backed by rectangular cavities. Some numerical results are compared with experimental data.